Air conditioning and refrigeration systems suffer from leaks. Within a year it is not unlikely that 30% of the refrigerant gas in the circuit will be lost. As there is a legal requirement of permanent monitoring for certain categories of systems (Regulation (EU) No 517/2014), we considered it appropriate to do some testing to allow the filling of the system to be done on time and without any surprises.
Using an ON/OFF contact and a permanently installed pressure sensor on the suction side, we were able to reliably observe the behavior of the circuit during manual removal and addition of refrigerant gas.
This system, in normal operation with the compressor active, has a circuit pressure of 3.6 – 3.7 bar.
When the refrigerant gas is removed, the pressure drop is obvious.
After tests, we came up with two alarms for this installation on the Arpedon Mechbase platform.
A Minor alarm at the level of 3.3 bar that works as a warning and a Major alarm at 3 bar.
Both alarms automatically generate work commands in the maintenance software (CMMS) that is installed on that installation to control the measurements.
If your installation includes air conditioning/ or refrigeration units, we can help you diagnose leaks with the permanent Arpedon Maintnode. systems in a timely manner.
Have a pump that makes popping sounds, or sounds like it’s pumping marbles? If so, you may have a cavitation problem.
Pump cavitation can cause a number of issues for your pumping system, including excess noise and energy usage, not to mention serious damage to the pump itself.
Description of the phenomenon
Simply defined, cavitation is the formation of bubbles or cavities in liquid, developed in areas of relatively low pressure around an impeller. The imploding or collapsing of these bubbles in areas where fluid pressure increases, causes intense shockwaves inside the pump, causing significant damage to the impeller and/or the pump housing.
If left untreated, pump cavitation can cause:
Damage to the pump housing, impeller and/or shaft
Excessive vibration level – leads to premature sealing loss and bearing failure
Higher than necessary power consumption
Decreased flow and/or pressure
There are also two phenomena that exhibit similar behavior to cavitation and is necessary to be reported: re-circulation and aeriation or air entrapment.
When a pump is in low pressure or high vacuum conditions, cavitation occurs. If the pump is “starved” or is not receiving enough flow, bubbles or cavities will form at the eye of the impeller. As the bubbles carry over to the discharge side of the pump, the fluid conditions change, compressing the bubble into liquid and causing it to implode against the face of the impeller.
An impeller that has fallen victim to suction cavitation will have large chunks or very small bits of material missing, causing it to look like a sponge. Damage to the impeller appears around the eye of the impeller.
Clogging of the suction area
Pump is running too far right on the pump curve
Poor piping design
Poor suction conditions (NPSH requirements)
When a pump’s discharge pressure is extremely high or runs at less than 10% of its best efficiency point (BEP), re-circulation of fluid occurs. The high discharge pressure makes it difficult for the fluid to flow out of the pump, so it circulates inside the pump. Liquid flows between the impeller and the housing at very high velocity, causing a vacuum at the housing wall and the formation of bubbles.
The implosion of those bubbles triggers intense shockwaves, causing premature wear of the impeller tips and pump housing. In extreme cases, discharge cavitation can cause the impeller shaft to break.
Blockage in the pipe on discharge side
The pump operates too far left on the pump curve
Poor piping design
AERIATION(OR AIR ENTRAPMENT)
Air entrapment happens when bubbles are in the liquid before reaching the impeller. This can happen when:
The liquid is aerated ( for whatever reason) near the pump inlet.
Liquid is near its boiling point, such as in a condensate pump.
While this problem is not always as damaging (or as loud) as the previous ones, it can certainly damage the impeller if left unchecked.
Preventive treatment actions
Check filters and the check valves – clogs on the suction, or discharge side can cause an imbalance of pressure inside the pump.
Reference the pump’s curve – Use a pressure gauge and/or a flowmeter to understand where your pump is operating on the curve. Make sure it is running at its best efficiency point. Running the pump off its best efficiency point not only causes excess recirculation, expect excessive heat, radial loads, vibration, high seal temperatures, and lowered efficiency.
Re-evaluate pipe design – Ensure the path the liquid takes to get to and from your pump is ideal for the pump’s operating conditions. Designs with inverted “U”s on the suction side can trap air, while designs with a 90° immediately before the pump can cause turbulence inside the pump. Both result in suction problems and pump cavitation.
Cavitation is a common problem in pumping systems, but with proper pump sizing, pipe design, and care of the whole system, damage to pumps can be largely avoided.
A satisfactory method to determine which of these problems are taking place using ultrasound or vibration analysis is to slow throttle the discharge valve closed.
As the discharge valve is being throttled closed:
If noise and vibration get better – expect cavitation.
If noise and vibration get worse – expect re-circulation.
If noise and vibration stay the same – expect aeriation (or air entrapment).
Assets with moving parts rely on the consistent application of lubricants to function properly. Facility managers who work to improve their condition monitoring strategies benefit from improved asset uptime and cost reductions. These two concepts go hand-in-hand. Lubrication is an essential facet of condition monitoring.
To ensure your program functions properly, avoid these five common lubrication mistakes:
You can have too much of a good thing. When an asset lacks grease, it will quickly make the problem known, usually by failing. At the other end of the spectrum, over greasing can have a similar effect. That’s why it’s important to remember that lubricants have volume of their own. Too much grease could actually cause an asset to jam, necessitating additional maintenance and hours of downtime.
Likewise, over-greasing may lead to seal failure. Grease guns can produce an extraordinary level of pressure, and, in excess, harm bearings. Similarly, when grease dries and cracks, the pressure of additional lubricant can cause it to break apart, further damaging the bearings. An ultrasound reading can help technicians know when enough is enough.
A lack of lubricant is likely one of the easiest problems to spot. Assets that aren’t properly maintained will make themselves known in short order. Typically, excess heat and sound will radiate from the asset until failure. Alone, these symptoms are easy to detect, but within a noisy facility, they could go unnoticed.
Ultrasound equipment such as the Ultraprobe® 201 Grease Caddy can help facilities save on operating costs by providing a visualization of ultrasonic waves. In doing so, personnel will know exactly when an asset needs lubricating and when it’s in working order. This process saves man-hours so they can be applied to situations of greater need. Plus, the device is easy to use, even in crowded and noisy environments.
3. Using the wrong lubricant
Not only can using the wrong lubricant lead to asset failure, but it may also void the machinery’s warranty. Machine manufacturers will typically recommend specific lubricants for each asset. These guidelines should be taken seriously, or else the money for a replacement will likely come from your department’s budget.
It’s also important to note that additives will change the composition and viscosity of your lubricants. If adding foam agents, antioxidants or corrosion inhibitors to your lubricant, check to see that it hasn’t altered to solution beyond the figures set by the asset’s manufacturer.
4. Mixing lubricants
Not all lubricants are created equal. In fact, mixing the wrong kinds of lubricants together can be just as damaging as not lubricating at all. According to Machinery Lubrication magazine, mixing synthetic and mineral-based lubricants can cause major problems, leading to leakages and complete failures.
According to the source, when the wrong lubricants mix, they risk expanding or shrinking nearby seals, causing them to fail. Such problems result in increased spending, as those assets must be replaced.
Similar problems occur when an incompatible thickener is added to grease. The mixture can become unstable and inappropriate for use on most machinery. The consistency of the lubricant may vary greatly and become unreliably. Not only does the machinery suffer as a result, but the grease must be tossed out too, leading to further expenses.
5. Lubricant contamination
One of the chief causes of premature bearing failure is lubricant contamination. Not only does contaminated lubricant harm machinery, but it can also be expensive to remove and clean. Understanding how and why contamination occurs is the first step to preventing premature failures. For instance, contamination may come from particles in the ambient air, dirt from outside the facility or from agents within the machine itself.
A condition monitoring policy that includes housekeeping protocols will ensure that contamination has a minimal impact on asset uptime. However, visual inspection may not be sufficient to determine if contamination has occurred. An ultrasound tool can pinpoint discrepancies in the ultrasonic output of a bearing, notifying maintenance personnel in well in advance of equipment failure.
An improved lubrication program starts with accurate data. Whether your facility utilizes a condition-based lubrication strategy or a preventive method, your technicians need more data if they’re going to make any progress.
The Ultraprobe® 401 Digital Grease Caddy Pro is the perfect blend of data management software and advanced digital technology. With this all-in-one device, your lubrication personnel can create baseline decibel levels, then take readings before and after lubrication to ensure the asset functions properly. In addition to solving these issues at their source, the device allows for quick cost calculations regarding the lubrication program.
The device is compatible with the Mechbase platform of ARPEDON.
For information on the Ultraprobe® 401 Digital Grease Caddy Pro, contact us.
Alarms in a diagnostic maintenance program are critical for the efficiency of the process. They show where the user’s attention should be focused.
This is because most machines in a plant do not show any problems. Eventually if the alarms are set correctly the user will deal with assets that have a real problem.
The simplest alarm method is the comparison of the current value with the base value. However, changes in the operation of the equipment (speed, load) or even environmental conditions changes, can affect the size that the sensors we use measure creating the risk of false alarms. These reduce confidence in the diagnostic maintenance system implemented by enhancing the risk of hiding real damage.
The international maintenance community is increasingly recommending the use of statistic methods for monitoring equipment to combat the phenomenon. The statistical analysis explains how much something can deviate from the ‘normal’ situation. This method is based on the notion of standard deviation or σ. The distribution of data is visually described by the following figure:
Measurements up to 1 x σ from the average, constitute the 68% of the measurements while measurements up to 2 x σ constitute the 95% of the measurements. As can be understood, data even further from the center are certainly indications that the machine’s operating condition is outside ‘normal’.
As part of the continuous improvement of our Mechbase software, we have added an assistant guide for the definition of statistical alarms.
The user having collected data with any of the supported methods, transitions to the measurement point. There they will come across the new option:
Then they will be asked to choose the measurement on which they will be based on. For oscillation measurements this might be RMS, Peak, Peak-to-Peak, Crest factor acceleration/velocity/offset. Regarding spectral analysis statistical alarms are also applied to arrange region value.
Based on the measurements selected, the guide suggests values for the alarms. At this point the used who is acquainted with the machine’s behavior may want to make changed and eventually finalize the alarms.
For a diagnostic maintenance program, the time spend on alarms is one of the most cost-effective throughout the program. We ensure that these costs are even lower by optimizing the outcome.
If you are interested in improving the reliability of your equipment click here.
Hellenic Recovery Recycling Corporation trusts ARPEDON’s MAINTNODE permanent systems as a part of a complete preventive maintenance program for 9 recycling plants. Permanent condition monitoring sensors where installed (ultrasound and acceleration) for the real time bearing supervision of the main production assets.
Moreover, the MAINTNODE system was configured for tracking the operation time of each asset independently. Hence, the ability is given for real time knowledge on the production performance as well as on the equipment structural status, via one system only.
The data are being collected in MECHBASE, ARPEDON’S online cloud platform. In this platform, the installation data for each asset is presented, with analytical diagrams of the sum of measurements. Also, alarms were set for each asset separately via the MECHBASE platform.
Finally, there was an integration of ARPEDON’S systems with HERRCO’s maintenance software (CMMS). That way, the maintenance staff workflow will not change as they will be using the tools they are used to (CMMS). It will be more informative though as they will receive additional information about the real condition of the equipment (productivity indicator-KPI’S and strain level of the machine parts).
For more information regarding the products, you can contact us either by phone or via our website’s contact form.
With the requirements to continually grow, it is important that the production line remains constantly at the optimum level of operation. Using new technologies and equipment maintenance practices, this is now affordable, easy and above all effective.
Analysis of the value of advanced maintenance techniques
Imagine that you installed a new packaging machine on your production line to pack large items, three months ago. For the packaging requirements of your production line, switch between the new machine and the existing old one. So during these three months you’ve packed 5,000 items in the new stack. However, the manufacturer proposes to change the bearings every three months or every 15,000 packages. Three months after the purchase of the machine, you have to make a precise (thorough) change of the bearings in order to comply with the manufacturer’s instructions. This is an example of preventive maintenance.
Analysis of the value of new maintenance techniques
Now, imagine that the machine you have installed has been inserted in your maintenance program. With a combination of sensors, you are constantly checking the state of your asset. Having used the packaging machine for 6 months and having packed 19,000 items, you receive a notice that you still have 1,000 packages until the next change of bearings is due. This is an example of predictive maintenance. Prevents damage and alerts you for maintenance work that is adapted to your own use for the equipment in advance before there is a risk of damage.
Preventive Maintenance VS Predictive Maintenance
Industrial sectors are already in accordance with the concept of preventive maintenance, but predictive maintenance has its own advantages which can enhance production.
Preventive maintenance work is carried out on the basis of time, events (facts-incidents) or even indications. The age of the equipment as well as the manufacturer’s recommendations are taken into account. In fact, preventive maintenance is a scheduled maintenance. However, as the example of the packing machine, this time-based maintenance approach probably it does not represent the actual condition of the equipment and it may lead to maintenance regardless if this maintenance is necessary according to the condition of the equipment and its components
On the other hand, predictive maintenance is based on actual equipment status instead of time factors. Using a combination of sensors, merging measurements and extracting features is performed. Classification is performed based on algorithmic predictions / or experts’ opinion damages can be predicted before being incurred, so ample time is given to the company to plan the maintenance. This allows field engineers to fix the damage before it ever occurs.
As is evident in predictive maintenance, advanced techniques and sensors are used, such as:
Oscillation sensors (Accelerometers) measure the motion of the camera and detect mechanical errors that are evolving.
Current analyzers monitor the status of the electrical components of the system.
Thermal remote images with mobile devices are used to access and store the temperature and infrared image of the production equipment.
Ultrasound sensors are used to detect leaks- inspect mechanical and electrical components.
Extension of Applications
What is the reason for using the preventive meeting since it has such positive results?
However, predictive maintenance offers significant cost savings by reducing downtime and lowering the cost of other parts and spare parts. Investing in a predictive maintenance system accounts for up to 10 times its cost to the oil and gas industry, according to a Roland Berge study.
One can easily and quickly measure points of interest even with multiple different sensors at the same time. In addition, one can access the state of the plant from anywhere and make decisions about their maintenance and operation. With the fixed systems and the Internet of Things (IOT), it is possible to repeat accurate and complete measurements in inaccessible or remote locations at any time without the need for staff relocation.
When the following are implemented on a software platform that is flexible and safe, the results are unsurpassed to the usual maintenance and tracking practices that exist to date. It is obvious that predictive maintenance is an attractive worthy investment that brings excellent results.